All liver diseases have common pathophysiologic characteristics with disease progression fueled by inflammation, accumulation of fibrosis, and alteration of the portal circulation. There are difficulties in monitoring hepatic function and portal blood flow in patients with liver disease. Such diseases include chronic hepatitis C, nonalcoholic fatty liver disease (NAFLD), primary sclerosing cholangitis (PSC), chronic hepatitis B, alcoholic liver disease, autoimmune liver disease, cryptogenic cirrhosis, hemochromatosis, Wilson's disease, alpha-1-antitrypsin deficiency, and cholestatic liver diseases.
Chronic Hepatitis C.
Two known liver function tests can be used to measure portal blood flow and were previously validated using a large cohort of patients with chronic hepatitis C. One such liver function test, called the FLOW test, accurately measures the portal blood flow from a minimum of 5 blood samples taken over a period of 90 minutes after an oral dose of deuterated-cholate. The FLOW test is disclosed in Everson, US 2010/0055734, Methods for Diagnosis and Intervention of Hepatic Disorders, filed Sep. 11, 2009, which is incorporated herein by reference. Another liver function test, the SHUNT test, comprises simultaneous administration of an intravenous dose of 13C-cholate and an oral dose of deuterated-cholate. The SHUNT test can be used to measure portal blood flow, and systemic hepatic blood flow and therefore determine the amount of portal-systemic shunting. The SHUNT test is disclosed in Everson et al., US2008/0279766, Methods for Diagnosis and Intervention of Hepatic Disorders, filed Jan. 26, 2006, which is incorporated herein by reference. A test that could more simply and rapidly estimate portal blood flow and hepatic function in patients with chronic hepatic C is desirable. A simple, efficient test for estimating portal blood flow is also applicable to other chronic liver diseases.
Nonalcoholic Fatty Liver Disease.
Non-Alcoholic Fatty Liver Disease (NAFLD) (Browning et al., 2004, Prevalence of hepatic steatosis in an urban population in the united states: Impact of ethnicity. Hepatology. 40: 1387-1395) may affect up to one-third of the US population and this vast epidemic is mostly hidden because people are usually asymptomatic and have normal ‘liver function tests’. The prevalence continues to rise along with the major risk factors which are obesity, metabolic syndrome, and insulin resistance. NAFLD can progress from simple fatty liver called steatosis, which is relatively benign, to the more serious NASH, Non-Alcoholic SteatoHepatitis. Hepatitis is inflammation of the liver and can also be caused by excessive drinking, as in Alcoholic SteatoHepatitis (ASH), or viral infection, i.e., Chronic Hepatitis C (CHC). All these chronic liver diseases (CLDs) are characterized by a similar patho-physiology with inflammation, cell death, and fibrosis leading to a progressive disruption of the hepatic microvasculature. About 5% of NAFLD patients will progress to cirrhosis (Adams et al., 2005, The natural history of nonalcoholic fatty liver disease: A population-based cohort study. Gastroenterology. 129: 113-121) and NAFLD will surpass CHC as the leading indication for liver transplantation.
Primary Sclerosing Cholangitis
The hallmark of PSC pathophysiology is portal fibrosis leading to portal hypertension (PHTN) earlier in disease compared to other etiologies of liver disease. The assessment of disease severity in PSC lacks a gold standard, as liver biopsy has significant sampling error and is no longer recommended. Hepatic Venous Pressure Gradient (HVPG) is invasive, expensive and impractical, and clinical models were really created to assess late-stage disease. There is an unmet need for accurate non-invasive assessment of PSC over the spectrum of disease severity.
Chronic Liver Disease.
Although chronic hepatitis C and NAFLD are the two most common chronic liver diseases in the US, a screening test for estimation of portal blood flow is desirable for patients having, or suspected of having, any chronic liver disease, such as, but not limited to, chronic hepatitis C, nonalcoholic fatty liver disease (NAFLD), chronic hepatitis B, primary sclerosing cholangitis (PSC), alcoholic liver disease, non-alcoholic steatohepatitis (NASH), autoimmune liver disease, cryptogenic cirrhosis, hemochromatosis, Wilson's disease, alpha-1-antitrypsin deficiency, and cholestatic liver diseases. Estimates suggest that 30 million or more Americans may be affected by chronic liver disease.
Difficulties in Monitoring Patients with Chronic Liver Disease.
Currently the only way to distinguish Non-Alcoholic SteatoHepatitis (NASH) from steatosis and to monitor NASH progression is through a needle biopsy, which assesses the grade of inflammatory activity and the stage of fibrosis. Biopsy is considered the gold standard despite suffering from numerous sources of inaccuracy and the risks of an invasive procedure. Patients must be sedated and a portion will experience bleeding and other complications (Janes and Lindor, 1993, Ann Intern Med. 118: 96-98; Seeff et al., 2010, Clin Gastroenterol Hepatol. 8: 877-883). The needle biopsy is a very small specimen of a very large organ and it is very difficult to obtain large enough pieces from enough locations for adequate sampling (Vuppalanchiet al., 2009, Clin Gastroenterol Hepatol. 7: 481-486; Bedossa et al., 2003, Hepatology. 38: 1449-1457; Regevet al., 2002, Am J. Gastroenterol. 97: 2614-2618). Biopsy interpretation is subjective and depends on the expertise of the observer (Rousselet et al., 2005, Hepatology. 41: 257-264) and the size and number of tissue samples (Rousselet et al., 2005; Vuppalanchiet al., 2009). In describing the progression of fibrosis in CHC the 6 stage Ishak system (Ishak et al., 1995, J. Hepatol. 22: 696-699) may be used, but more typical is a simpler 4 stage system (Knodell et al., 1981, Hepatology. 1: 431-435; Batts and Ludwig, 1995, Am J Surg Pathol. 19: 1409-1417; Scheuer, 1991, J. Hepatol. 13: 372-374) such as Metavir (Group, TFMCS, 1994, Hepatology. 20: 15-20) which is very comparable to the 4 stage system used for NASH (Brunt et al., 1999, Am J. Gastroenterol. 94: 2467-2474; Kleiner et al., 2005. Hepatology 41: 1313-1321). However, the heterogeneity of lesions in NASH decreases the accuracy (Ratziu et al., 2005, Gastroenterology. 128: 1898-1906). It is not practical to biopsy a third of the population especially since the method has an estimated error rate of 20% or greater. Other standard liver blood tests are not very useful. Liver enzymes such as ALT or AST may spike during activity flares, but often they are in the normal range due to the slow rate of progression. The liver's production of albumin or clotting factors only declines at the latest stages of CLD. Noninvasive means to distinguish NASH from steatosis and accurately monitor NASH progression are desirable.
Deficiencies of Other Non-invasive Test Methods.
The need for non-invasive liver assessment has led to the commercialization of new methods including biomarker panels, metabolic breath tests, and transient elastography. Biomarker panels (Mukherjee and Sorrell, 2006, Noninvasive tests for liver fibrosis. Semin Liver Dis. 26: 337-347; Shah et al., 2009, Comparison of noninvasive markers of fibrosis in patients with nonalcoholic fatty liver disease. Clin Gastroenterol Hepatol. 7: 1104-1112) such as FibroTest® are not sensitive enough to detect either early stage CHC (Boursier et al., 2009. Improved diagnostic accuracy of blood tests for severe fibrosis and cirrhosis in chronic hepatitis c. Eur J Gastroenterol Hepatol. 21: 28-38; Shaheen et al., 2007, Fibrotest and fibroscan for the prediction of hepatitis c-related fibrosis: A systematic review of diagnostic test accuracy. Am J. Gastroenterol. 102: 2589-2600) or NASH (Ratziu et al., 2006, Diagnostic value of biochemical markers (fibrotest-fibrosure) for the prediction of liver fibrosis in patients with non-alcoholic fatty liver disease. BMC Gastroenterol. 6: 6; Angulo et al., 2007, The NAFLD fibrosis score: A noninvasive system that identifies liver fibrosis in patients with NAFLD. Hepatology. 45: 846-854; Wong et al., 2010, Diagnosis of fibrosis and cirrhosis using liver stiffness measurement in nonalcoholic fatty liver disease. Hepatology. 51: 454-462) or to track progression because circulating proteins/fragments can't report accurately on fine structure, the disruption of the microvasculature, and impairment of flow.
Metabolic tests are variable because they rely on CYP enzymes which vary according to gender, age, genetics, diet, medications and they are insensitive to early stage disease because the enzymes do not significantly decline until later stages. BreathID® has a methacetin metabolic test in FDA trials, but this method failed to detect early stage CHC in earlier studies (Braden et al., 2005. 13c-methacetin breath test as liver function test in patients with chronic hepatitis c virus infection. Aliment Pharmacol Ther. 21: 179-185).
FibroScan®, also in FDA trials, uses transient elastography to measure liver stiffness to estimate fibrosis (Del Poggio and Colombo, 2009. Is transient elastography a useful tool for screening liver disease? World J. Gastroenterol. 15: 1409-1414). This method is insensitive to early stage CLD (Del Poggio and Colombo, 2009, infra; Friedrich-Rust et al., 2008. Performance of transient elastography for the staging of liver fibrosis: A meta-analysis. Gastroenterology. 134: 960-974) including CHC (Shaheen et al., 2007, infra, and Rossi et al., 2003. Validation of the fibrotest biochemical markers score in assessing liver fibrosis in hepatitis c patients. Clin Chem. 49: 450-454) or NASH (Wong et al., 2010, Diagnosis of fibrosis and cirrhosis using liver stiffness measurement in nonalcoholic fatty liver disease. Hepatology. 51: 454-462) and is compromised by obesity, a major risk factor for NAFLD. More effective noninvasive means to distinguish NASH from steatosis and accurately monitor NASH progression are clearly needed.
A method for estimating portal blood flow and hepatic function in a subject is provided. The herein disclosed single-point STAT test is a simplified, convenient test intended for screening purposes that can reasonably estimate the portal blood flow from a single blood sample taken at, e.g., 60 minutes after orally administered deuterated-cholate. All liver diseases have common pathophysiologic characteristics with disease progression fueled by inflammation, accumulation of fibrosis, and alteration of the portal circulation. Because STAT provides an accurate estimate of portal blood flow, the test is developed as a diagnostic with application for all liver diseases. Liver diseases for which the STAT diagnostic could be utilized include, but are not limited to, chronic hepatitis C, nonalcoholic fatty liver disease (NAFLD), primary sclerosing cholangitis (PSC), chronic hepatitis B, alcoholic liver disease, autoimmune liver disease, cryptogenic cirrhosis, hemochromatosis, Wilson's disease, alpha-1-antitrypsin deficiency, and cholestatic liver diseases. STAT can be administered as an in vitro screening test to a patient having, or suspected of having, any chronic liver disease.
The non-invasive test methods disclosed herein are superior to each of these competitors in the abilities to detect early stage CLD and accurately monitor disease progression of, e.g., chronic hepatitis C, primary sclerosing cholangitis (PSC), nonalcoholic fatty liver disease (NAFLD), chronic hepatitis B, alcoholic liver disease, autoimmune liver disease, cryptogenic cirrhosis, hemochromatosis, Wilson's disease, alpha-1-antitrypsin deficiency, and cholestatic liver diseases. In a specific embodiment, the single-point STAT test is used as a screen to evaluate disease progression of chronic hepatitis C (CHC), primary sclerosing cholangitis (PSC) and Non-Alcoholic Fatty Liver Disease (NAFLD).